The present invention relates to a transfer device for a substrate, more specifically a transfer device for a substrate capable of preventing deformation or breakage due to bending stress, by reducing the amount of substrate dead weight deflection in items such as large mother glass boards, etc., which includes a storage device.
Mother glass boards such as liquid crystal, etc. are stored in special storage devices such as mother glass board storing cassettes, etc., so they may be stored separately to avoid contact with one another. The mother glass board storage cassette is used for both transporting and temporarily storing liquid crystal mother glass boards between manufacturing systems, for example, on large mother glass board manufacturing lines.
The mother glass board storage cassette is provided with a plurality of supporting members 3a′, 3b′ disposed in parallel in opposite directions, extending from two side walls 2a, 2b of a box-shaped cassette body 1, as shown in FIG. 9. It is designed in such a way as to introduce or remove mother glass boards 5 by raising and lowering a hand 4′ of a transfer machine inserted in the cassette body 1 between the supporting members 3a′, 3b′. 
The cassette body 1 requires a large space at the center, in the direction of the breadth of the cassette body 1, to enable the raising and lowering of the dichotomous fork-shaped hand 4′. It is therefore formed in such a way that the supporting members 3a′, 3b′ protrude a comparatively short distance from the left and right side walls 2a, 2b. In such case, it is arranged so that the mother glass boards 5 stored in the cassette body 1 are supported by the supporting members 3a′, 3b′ provided extending from the left and right side walls 2a, 2b of the cassette body 1, to reduce dead weight deflection of the mother glass boards 5 stored there.
Moreover, for the hand 4′ of a transfer machine used to introduce and remove the mother glass boards 5 to and from the cassette body 1, the dimension L in the direction of the breadth of the hand 4′ is fixed to avoid an increase of mother glass board 5 deflection when the mother glass boards 5 are raised with the hand 4′.
However, with the progress in recent years of a general trend toward larger and thinner mother glass boards, even mother glass boards of high rigidity have come to produce excessive deflection. As a result, with the conventional mother glass boards storing cassettes, the length of supporting members is restricted to short distances, the dead weight deflection of mother glass boards 5 has increased and the mother glass boards themselves are subject to increased bending stress because of this deflection, presenting problems of deformation or breakage.
Thus, as shown in FIG. 10, while the mother glass board 5 stored in the cassette body 1 is subject to a large dead weight bending force as the size of the mother glass board 5 becomes larger than that in FIG. 9, the dimension 1 in the direction of the breadth of the hand 4′ must be reduced to allow the supporting members 3a′, 3b′ to extend to the center in the direction of the breadth of the mother glass board 5 to correct this bending.
However, if the dimension 1 in the direction of the breadth of the hand 4′ is reduced, the deflection of the mother glass board 5 placed on the hand 4′ becomes as indicated by the dotted line in FIG. 10 (c). The mother glass board 5 is then subject to a great bending force, allowing it to be easily deformed or broken.